In the Sierra Nevada,there are a large number of sympatric and ecologically similar seed-caching rodents.Their ability to coexist has been assumed to occur through resource partitioning.However,no study to date has shown the effects of resource partitioning to be sufficient to explain how multiple species of seed-caching sciurids and cricetids coexist.Another behavior among seed-storing rodents,cache pilfering,could allow rodents to alleviate resource-partitioning differences.In this study,we hypothesized that there would be no difference in pilfering ability among seed-caching rodents (reciprocal pilfering) or if pilfering is not equal,a difference in caching behavior will be present.If neither is true,the species with a pilfering advantage could potentially outcompete ecologically similar rodents and eventually extirpate them.It is unlikely that this scenario of unequal pilfering by itself could lead to the diversity of seed-caching rodent communities of the Sierra Nevada.To address this question,we examined the pilfering ability of four coexisting seed-caching rodent species: Tamias amoenus,T.quadrimaculatus,Peromyscus maniculatus,and Callospermophilus lateralis.Both species of Tamias and P.maniculatus are scatter-hoarders while C.lateralis is a larder-hoarder.Trials (n=48) of pair-wise comparisons were conducted to determine how well na (i) ve individuals could locate and retrieve caches created by other rodents inside a large field enclosure.No significant differences were observed among either Tamias spp.and P.maniculatus,supporting reciprocal pilfering.Callospermophilus lateralis were unable to pilfer any caches from other species; this is likely due to their habit of larder-hoarding and pilferage avoidance.